This invention is directed to a disk drive device; more specifically, it is directed to a device for loading disk drive read-write heads onto a medium.
Over many years, a variety of devices that read and write information on a rotating disk medium have been developed and used as computer data storage devices. Of these devices, magnetic medium devices have been, and still are among, the most common computer storage devices. Widely used magnetic disk drive devices are generally available in two broad categories-removable and fixed. In particular, removable cartridge disk drives read and write information magnetically on a disk that is enclosed in a removable protective case. By contrast, fixed disk drives read and write information magnetically on a fixed disk that is permanently fixed in the data storage device.
Fixed disk drives are used as the principal data storage devices of computers, since they typically have data transmission speeds and storage capacities that are several orders of magnitude greater than removable disk drives. Fixed disk drives have the drawback, as compared with removable disk drives, in that the disk cannot be easily moved to another computer. As a result, it is ordinarily desirable to provide computers with both a removable disk drive along with a fixed disk drive, and most desktop computers have both.
In recent years, however, mobile computers of very small sizes, such as hand held, notebook and lap-top computers, have become widely used. Because space in these computers is a premium, removable cartridge disk drives are attached externally or not at all. Furthermore, in such small computers, external removable cartridge drives are very inconvenient for mobile use. Hence, many of these types of computers do not have disk drives, but rather use IC card based storage media via a PCMCIA port on the computer. However, since IC cards use semiconductor memories, storage capacities are small, and costs are high. These drawbacks have made it difficult for such computers to use programs and data that have large storage requirements.
In response to the widespread use of small size mobile computers, smaller disk drives have been, and are, under development. Such drives present many development challenges including size and power constraints. The storage density is high and the components are smaller and potentially more delicate making them susceptible to damage. Moreover, small portable drives are likely to be battery powered and may share that battery power with a primary device such as a hand held computer.
Loading the head onto the surface of the data storage medium is a critical part of the design of magnetic storage medium. In order to ensure successful loading of the head onto the medium, a relatively high voltage and current is typically used. The duration and value of this current is typically set at a high value to ensure successful head loading for all drive systems. Each drive typically has it own drive characteristics, such as friction and stiction forces of the actuator arm in contact with the load ramp, that must be overcome by the drive head load characteristics in loading the head. A drive having set drive head load characteristics result in some instances in the heads failing to load onto the medium because the set head load characteristics of the drive are not sufficient to overcome the drive characteristics. More importantly, the set head loading characteristics, such as voltage and current, result in other instances where the heads load onto the medium with an excessive head load velocity. These excessive head load velocities cause damage to the head, the medium, or both.
Typically, the heads and the medium surface in magnetic storage devices are highly susceptible to damage. For example, small amounts of debris have been known to render drives and medium useless. Similarly, loading the heads onto the medium surface has the potential to damage the heads, the medium, or both. Moreover, loading the heads in small, high capacity device must also meet power and size constraints without causing damage to the drive or storage medium.
Therefore, there is a need to provide a head loading apparatus and method that may adapt to the load characteristics of each disk drive device. Particularly, a disk drive device that is small and portable.
In order to meet the aforementioned need, this invention provides a head loading apparatus for a disk drive device that reads data from and writes data to a magnetic medium. The head loading apparatus comprises an actuator movably disposed within the disk drive and a read-write head in mechanical communication with the actuator. The actuator moves the read-write head in response to an electrical signal. The head loading apparatus also comprises a head load ramp for loading and unloading of the read-write head between the disk medium and a parked position off of the medium and means in electrical communication with the actuator for moving the heads from the parked position to the medium by applying an electrical signal. The signal is adaptive in an increasing and decreasing manner in response to a measured head load velocity, such that the heads move off of the load ramps toward the medium at a minimal velocity.
The adaptive soft head loading is achieved by adapting a characteristic of the disk drive head loading operation, preferably an electrical signal, to correspond to the individual load characteristic of a particular disk drive. More preferably, the pulse width of an electrical signal is adaptive in an increasing and a decreasing value, such that the pulse width is a minimal pulse width required to move the heads into soft engagement with the medium. More preferably, the pulse width is adapted between at least two different pulse width points. Preferably, one of the pulse width points approaches, without exceeding a pulse width upper limit, which corresponds to a head loading velocity limit. The other pulse width point preferably approaches without falling below a pulse width lower limit. This adaptive soft head loading substantially ensures successful head load, while at the same time allows the head to be loaded into engagement with the medium at a safe velocity, thereby reducing the potential for damage to the head, the medium, or both.